Covalent inhibitors of coronavirus papain-like protease

A compound having the following structure:

• wherein:
• R1 is a linker having the formula —(CH2)n-L1-, wherein L1 contains 1-6 carbon atoms and at least one —NH— linkage and at least one oxygen-containing or sulfur-containing linkage, and n is an integer of 0-3;
• R2 is a group having the formula —C(Y)-E, wherein Y is O or S, and E is a hydrocarbon group containing 1-12 carbon atoms and either:
• (i) at least one carbon-carbon or carbon-nitrogen unsaturated bond or (ii) at least one alkyl halide group;
• R3 is selected from the group consisting of H, NR′2, NHC(O)R′, and —(CH2)p-T, wherein T contains at least one —NH— linkage;
• R′ is independently selected from H and hydrocarbon groups containing 1-6 carbon atoms;
• and p is an integer of 0-3;
• Ra, Rb, Rc, Rd, Re, and Rf are independently selected from the group consisting of H, hydrocarbon groups containing 1-3 carbon atoms, fluorine atom, and chlorine atom;
• X is N or CR9, wherein R9 is selected from the group consisting of H, hydrocarbon groups containing 1-3 carbon atoms, fluorine atom, and chlorine atom;
• and pharmaceutically acceptable salts thereof.